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Get familiar with the reaction system: Introducing the Reaction System
MCM 55-5650
So have a pair of these in-hand.
Sample 1 in blue, sample 2 in red:
Note the scale - very little rise in impedance above resonance. Copper cap is doing its thing.
Reasonably close to each other. Less than 1/2db off in calculated sensitivity, and said sensitivity being higher than advertised so that's cool.
High Q, high Fs = probably best as dedicated midrange (which is where it is going).
Sample 1 in blue, sample 2 in red:
Note the scale - very little rise in impedance above resonance. Copper cap is doing its thing.
Sample 1 parameters:
Fs = 97.65 Hz
Re = 5.98 ohms[dc]
Le = 22.35 uH
L2 = 105.00 uH
R2 = 1.28 ohms
Qt = 1.11
Qes = 1.70
Qms = 3.17
Mms = 1.69 grams
Rms = 0.327184 kg/s
Cms = 0.001572 m/N
Vas = 2.91 liters
Sd= 36.32 cm^2
Bl = 1.907908 Tm
ETA = 0.15 %
Lp(2.83V/1m) = 85.22 dB
Sample 2 parameters:
Fs = 95.20 Hz
Re = 5.98 ohms[dc]
Le = 22.61 uH
L2 = 96.73 uH
R2 = 1.23 ohms
Qt = 1.07
Qes = 1.65
Qms = 3.02
Mms = 1.55 grams
Rms = 0.307454 kg/s
Cms = 0.001798 m/N
Vas = 3.33 liters
Sd= 36.32 cm^2
Bl = 1.834964 Tm
ETA = 0.17 %
Lp(2.83V/1m) = 85.60 dB
Added Mass Method:
Added mass = 5.00 grams
Diameter= 6.80 cm
Reasonably close to each other. Less than 1/2db off in calculated sensitivity, and said sensitivity being higher than advertised so that's cool.
High Q, high Fs = probably best as dedicated midrange (which is where it is going).
Very nice cast frame, well thought out IMHO.
I have a signature.
Comments
For now, a single axis measurement plus a distortion sweep:
The odd spike around 450Hz might be my furnace, might be something else. Who knows. That SPL level is accurate - no two ways about it, the shorting rings are doing their job on this little guy.
The yellow line is the midrange, in-box, with rear chamber. The red line is the little tweeter, and the gray line is the 6.5" KB woofer.
Sooo... the midrange is definitely a low distortion design. It suffers from similar FR problems that plague some other little drivers, notably the region from 1.8 to 4k. However, it is not something I am going worry about because the performance is excellent elsewhere.
Only thing I *might* be concerned about is the low sensitivity - might be doing more overlap between woofer and tweeter than I originally intended.